A new radionuclide scintigraphic technique will be employed to study the regulation of gallbladder emptying. The aims of this study will address the following questions. 1) What are the effects of chemical and physical composition of meals on gallbladder emptying responses? Monocomponent and multicomponent meals will be studied. The effects of solid versus liquid meals and isotonic versus hypertonic meals will be determined. 2) What are the effects of pharmacologic agents on gallbladder emptying? Alpha and beta adrenergic and cholinergic agonists and antagonists will be evaluated. 3) Can gallbladder emptying be stimulated or inhibited by administration of gastrointestinal peptides? Dose-responses to cholecystokinin, secretin, glucagon and somatostatin will be studied. 4) Is gallbladder emptying affected by endogenous autonomic stimulation? Vagal cholinergic responses will be stimulated by sham feeding and insulin-induced hypoglycemia and an alpha adrenergic response, by cold-pressor testing. 5) Does alcohol affect gallbladder emptying? Both the gallbladder response to oral alcohol and the effect of oral alcohol on the gallbladder emptying response to meals will be investigated. Dose-response curves will be established. 6) Is gallbladder emptying abnormal in patients with selected disorders? Patients with cholelithiasis, diabetes mellitus, vagotomy, and biliary dyskinesia will be tested. The mechanism of abnormal emptying, if observed, will be studied.